SOCIO-ECONOMIC ASPECTS OF
WASTEWATER TREATMENT AND WATER REUSE
Bahman Sheikh, PhD, PE, Water Reuse Specialist
San Francisco, California USA
[email protected]
ABSTRACT
Wastewater treatment is an essential prerequisite for water reclamation and reuse. Proper
treatment and disinfection of wastewater is also a public health necessity in human
communities. Treatment and distribution of recycled water involves great expenditure of
resources, which in many developing countries is either lacking or is devoted to more
urgent national priorities. Also, an appropriate valuation of water and its benefits to
society is often lacking due to a misperception of abundance and taking water for
granted—a gift of nature, to be used at will. This attitude must be changed with proper
educational tools if the relatively constant amounts of water now available are to be
sufficient for increasing populations of the future.
Water reuse projects face additional impediments. One major impediment is that the
agreement of two or more governmental entities are required before a project can be
implemented. These institutional barriers are not insurmountable, but they involves
lengthy negotiations and much give-and-take on the part of the involved entities. Ideally,
a single entity would be managing all matters related to the entire water cycle, but this is
rare. Pricing of recycled water is another issue complicating the ability of water
managers to pay the costs of implementing water recycling projects. Recycled water is
often priced significantly below the price of potable water.
Public attitudes toward reuse of reclaimed water for non-potable applications is generally
positive. However, there have been several instances in California and Australia where
resistance to indirect potable reuse has derailed a few otherwise excellent projects.
Fortunately, public outreach and educational programs have been devised by
professionals in the field for early public involvement and prevention of dissemination of
misinformation by project opponents. The effects of global warming on future water
supplies is not expected to be uniform everywhere, but it will be drastically limiting in
certain parts of the arid and semi-arid regions of the world. Already, the continent of
Australia is experiencing a ten-year drought, attributed to global warming. This increases
the urgency for development of water use efficiency measures, such as water recycling in
these regions.
1.
INTRODUCTION
Protection of the public health is the prime reason for providing a supplemental source of
water supply—recycled water. The entire process of treatment, distribution and final use
of recycled water must, therefore, be also highly protective of the public health.
Until the latter part of the 20th Century, decisions about public water supply resources
were made strictly by engineers and other experts. There was virtually no consultation
with the public at large regarding their preferences, the impacts of such decisions, or the
relative merits of various resources considered for development. In recent years, the
public has become involved increasingly with water supply decisions and planning for
future water resources for the community. The greater involvement of the public in such
decisions—at least in the industrialized nations of the world—has exerted an immense
impacts on the nature of the decisions, length of time needed to implement a water
project, and especially on the use of water reclaimed from wastewater for reuse.
The socio-economic impacts of wastewater treatment and reuse have always been an
integral part of wastewater management decisions. In the past, the impacts became felt
long after it was too late to go back and make a better decision. Only in recent years have
these impacts come to the forefront of decision-making and selecting options for the
future.
2.
RECOGNIZING THE FULL VALUE OF WATER
At the heart of the public involvement in water matters is an awakening awareness of the
real value of water on the part of the general public. While this awareness is not
widespread yet, it is spreading. The fact that middle- and lower-class individuals now
routinely pay for bottled water over 1,000 times more than the cost of tap water is an
indication of their willingness to pay for the higher quality drinking water. This is in
spite of the fact that municipal tap water is, in most cases, comparable to any bottled
water on the market in microbial and chemical quality. To convince the same public to
pay a fair price for municipally provided tap water requires a herculean effort involving
service improvement, reliability of continuous water supply at the proper pressure,
assurance of high quality and safety of the served water, and trust in the system providing
public water service. Obviously, this cannot be accomplished overnight. But, without a
conscious effort, it is hard to imagine that it would ever be accomplished on its own
accord.
In many developing countries, there is a strong and widespread reluctance to pay for
water service, even among those who can afford the relatively low costs involved.
Collection of fees for wastewater treatment and proper disposal or reuse is even more
difficult, because the service is often not perceived as necessary, beneficial, or resulting
in immediate satisfaction of any desire on the part of the rate payers. This results in a
vicious cycle of poor service, dissatisfaction with the poor service, and greater lack of
desire to pay for that poor service. This cycle of perpetuating degradation of service is
graphically illustrated in Figure 1. It explains why so many communities lack a safe
potable water service and a proper wastewater management system. The cycle underlies
the difficulty of reclaiming the
wastewater and treating it to a high
enough level that would make it suitable
for a variety of beneficial reuse.
Figure 1. The Vicious Spiral of Low Funding
SOURCE: Pacific Institute
3.
PUBLIC PERCEPTIONS OF WATER REUSE
The public generally does not think much—if at all—about the origins of its water
supply; however, there is an assumption of purity and virginity associated with potable
(drinking) water that defies reality. The reality is that all water is recycled and there is
virtually no “new” water created and no naturally occurring water is “pure”. With human
and animals interacting with water, with urbanization and industrialization, nearly all raw
water supplies are contaminated biologically and chemically. This information, plus the
capability of technology to take contaminants out of any source of water and return it to a
safe and pure status must be communicated to a community on the verge of adopting
expensive wastewater treatment and water reuse—as shown in Figure 2, adapted from
Asano et al i . Otherwise, the public’s reluctance to pay, their aversion to recycling of
water by technological means, and the mistrust of utilities to use public money honestly
and efficiently will prevent
realization of the water cycle
High
projects.
Over the coming years, giant strides
will have been taken by WateReuse
POTABLE
WATER
SOURCE WATERS
A graphic depiction of changes of
water quality with treatment stages is
presented in Figure 2. This depiction
is primarily aimed at biological
quality of the water, but it can also be
used to convey changes in the
chemical constituents in water and
wastewater as it undergoes use, reuse,
treatment, and further treatment.
ADVANCED
RECYCLED
WATER
GRAY WATER
WASTE WATER
Low
PRIMARY
EFFLUENT
TERTIARY
RECYCLED
WATER
SECONDARY
EFFLUENT
Increasing Levels of Treatment, Monitoring, Enforcement, Safety Measures
Figure 2. Change in Water Quality with Use and with
Treatment Levels
Adapted from Asano et al., 2006
Association and its research arm, the WateReuse Foundation in solving the difficult
problem of overcoming public apprehensions about use of recycled water. Already,
several guidebooks and special projects have been completed ii , iii , iv . Research projects to
further delineate public response to wastewater treatment and water reuse have been
funded and are “in the pipeline”. These projects will bear fruit over the coming decades
and result in a much more systematic approach to public education and outreach during
the planning process for water recycling projects.
4.
PRICING RECYCLED WATER
Recycled water is generally priced below potable water to provide a significant incentive
for customers to switch from potable to recycled water. The extent of discount ranges
from 15 percent to as high as 100 percent—giving the recycled water free of charge to the
users, in cases where the agency desperately needs a reliable disposal venue. This
requirement for discounting the price of reclaimed water places one more impediment on
implementation of new water reuse projects: inability (or difficulty) to repay the costs of
project implementation, operation, and maintenance. Because of the significant benefits
of water reuse to society and the environment, incentive subsidies are often provided by
regional and central governments to local governments to overcome these fiscal
imbalances. This is a means by which the larger society pays for the benefits derived
from every water reuse project implemented by local governmental agencies.
The pricing schemes for potable water are generally below the actual cost of operation
and maintenance —not to mention the capital costs of constructing the treatment and
distribution systems—of the supply systems in many communities. Thus, the even lower
price of reclaimed water cannot be expected to cover the normal costs of operating a
water reuse system. Subsidies, incentive payments, and transfers from other funds are
commonly used to defray the gap between cost and revenue of water reuse systems.
5.
INTERAGENCY COLLABORATION AND
AGREEMENTS
Several agencies with different authorities and responsibilities must come together and
form an agreement before a water reuse project can be initiated in a community.
At the national level, the departments of agriculture, public health, finance, water
resources, and the environment are involved and each have a jurisdictional authority over
the project. At the local level, the agreement must be reached among water wholesalers,
retailers, wastewater managers, and public works officials. These multi-agency
agreements are difficult at best and impossible at worst. A strong motivation for the
agencies to agree to cooperate must come from one of the following sources of pressure:
•
Water scarcity and a public health crisis situation arising from deficiency of water
•
Environmental impact of discharge of treated wastewater, loss of threatened and
endangered species of plants and/or animals
•
Need for increasing the reliability of water supply and independence from
imported sources of water
Each of these motivators or a combination of several of them can be strong enough to
move the diverse parties to the negotiating table and eventually make it possible to start a
water recycling program. Another possible motivation is the anticipated effects of global
warming on water supplies—discussed further in Section 6, below.
The greater the number of agencies involved in decision-making regarding a new water
reuse project, the longer it takes to accomplish the necessary tasks, reach agreement, and
complete the project. In a recent study of over 200 California water recycling projects,
an inverse relationship was discovered between the number of “intermediaries” (between
the producer and the final customer of recycled water) and the volume of water reclaimed
and reused v . A similar relationship was also found between the number of intermediaries
and the number of successful projects in operation. These relationships are graphically
depicted in Figure 3.
400
400,000
LEGEND:
Green Line: Volume of Water—Left Scale
Blue Line: Number of Projects—Right Scale
300,000
350
300
250,000
250
200,000
200
150,000
150
100,000
100
NUMBER OF WATER RECYCLING PROJECTS
VOLUME OF WATER RECYCLED, AFY
350,000
50
50,000
0
0
0
1
2
3
NUMBER OF INTERMEDIARIES
Figure 3. Relationship between Number of Intermediaries and Number of Successfully Implemented
Projects, and the Volume of Recycled Water Generated.
6.
GLOBAL WARMING
Global warming 1 as affected by human activity since the onset of the industrial
revolution is accepted as a phenomenon of grave concern by climate scientists. The
phenomenon is questioned by some with a vested interest in the short-term economic and
1
Climate change is a euphemistic reference to the same phenomenon for those uncomfortable with the
massive evidence for global warming or for the role of humans in the accelerated rate of warming of ocean
waters, atmosphere, and the gradual melting and disappearance of continental glaciers.
political consequences of decisions that may lead to a reversal of recent (last two
centuries) trends in the concentration of carbon dioxide in the earth’s atmosphere.
However, decisions to reduce carbon emissions are necessary if planet earth is to remain
hospitable to human existence for the foreseeable future.
One of the critical (and relatively immediate) effects of global warming is expected to be
a major elevation of temperatures throughout the world, resulting in higher
evapotranspiration rates, directly leading to increased demand for irrigation water.
Irrigation of agricultural lands accounts for over 75 percent of the demand for water in
countries in the arid and semi-arid regions of the world. A global-warming induced
increase in demand for water—not balanced by an equal increase in supply—would be
terribly stressful on available sources of water supply and will likely increase the
motivation for implementation of water conservation and recycling programs. After all,
recycled water is a local source of water, most readily available to the urban sector, at
least for nonpotable applications. Potable applications are on the horizon; Namibia,
Singapore, and Australia are leading the way.
7.
NEED FOR STORAGE OF RECYCLED WATER
Recycled water is generated at a
relatively steady pace and does not
require as much storage as does
precipitation occurring in only a few
months of the year. If used for
agricultural irrigation, recycled water
receives less treatment than if used for
indirect potable use. However, it will
need large storage volumes to balance
seasonal demand against year-round
supply. Figure 4 shows a groundwater
recharge basin and pump station for
Figure 4. Groundwater recharge of reclaimed water
recycled water from the City of Tel
for treatment, storage, and agricultural irrigation, in
Aviv, Israel. The aquifer-stored water is Israel
pumped from wells and sent to Negev
Desert (50 kilometers away) for unrestricted irrigation of a variety of crops. Israel
recycles over 70 percent of its wastewater in planned and managed projects. Unplanned
reuse of wastewater and wastewater effluent (by way of withdrawals from local streams
dominated with upstream wastewater discharges) is common and sometimes approaches
100 percent of the discharge in some countries. However, this practice is not protective
of the public health and is not considered a sustainable water reuse policy.
If highly treated recycled water is used for direct potable purposes—rather than for
landscape irrigation—the demand will be matched by supply and there will be no need
for seasonal storage. Indirect potable reuse, on the other hand, involves augmentation of
surface reservoirs or groundwater aquifers. Thus, storage capacity is needed to provide
the necessary mixing and detention time.
8.
SUSTAINABLE WATER RESOURCES PLANNING
Most water resource planners now recognize the importance of integrated water resources
planning, taking into account a variety of sources of water, rather than just one or two
traditional sources. It is no longer unusual for an agency to have access to a number of
well-defined sources of water supplies from one or more of the following categories:
•
Imported water from far away
•
Imported water from a neighboring watershed, transfers, and exchanges
•
Local surface runoff, stored in surface storage reservoirs
•
Local groundwater resources used within a safe-yield management plan
•
Local groundwater resources used to extinction—not a sustainable resource, but
sometimes an inevitable short-term or interim solution
•
Water conservation through a variety of water use efficiency measures
•
Water reclamation, recycling, and reuse
•
Desalination of brackish water or seawater
Each one of these water supply sources can play a vital role in a given community’s
integrated water resources plan, managed with full recognition of its limitations, water
quality, environmental impact of its utilization, and other services and benefits related to
each resource. Bringing recycled water into the supply mix initially may represent a
small fraction of the total water demand, or it may be a significant portion of the supply,
depending on local circumstances. Either way, its presence in the overall mix will
improve dependability of supply of water and will release much needed potable supply
from the irrigation sector.
An important attribute of recycled water is that its availability and quantity increases with
increasing population—quite the opposite of the trend for other resources, which are
either diminishing in quantity, or quality, or both, as a direct function of population
increase. Therefore, provisions for inclusion of this sustainable source of water in the
community’s integrated water resources plan is a wise and visionary step.
REFERENCES
i
Takashi Asano et al., 2996 Water Reuse Issues, Technologies, and Applications, McGraw Hill, New
York, p. 29
ii
WEF / AWWA, 1998, “Public Information Outreach Programs”, Chapter 6 in Using Reclaimed Water to
Augment Potable Water Resources, Alexandria, Virginia, Denver, Colorado
iii
Lois Humphreys, 2006, “Marketing Nonpotable Recycled Water: A Guidebook for Successful Public
Outreach and Customer Marketing”, WateReuse Foundation, Alexandria, Virginia.
iv
John Reutten, 2004, “Best Practices for Developing Indirect Potable Reuse Projects:Phase 1 Report”,
prepared by Resource Trends, Inc. for WateReuse Foundation, Alexandria, Virginia.
v
Bahman Sheikh et al, 2004 “Institutional Requirements in California and Florida for Implementation of
Water Recycling/Reclamation Projects”, Presented at WateReuse Symposium XIX, Phoenix, Arizona.
Recycled water used for landscape irrigation, lakes, and golf course fairways,
Silver Lake Country Club, California